Mystery Solved, Thanks to Insects

Michigan State University entomologist and osteopathic medical specialist Eric Benbow is performing cutting-edge research that blends entomology and microbiology to solve mysteries in areas as diverse as aquatic ecosystem dynamics and homicide investigations.

Benbow, who came to MSU in 2014, is partnering with Carl Schmidt, associate professor of pathology at the University of Michigan and Wayne County Medical Examiner, for a three-year project through a grant from the U.S. Department of Justice. He and his team are assisting death-scene investigators with the forensic analysis of homicide victims in Detroit.

Blowflies and the Necrobiome

It has long been understood that the population dynamics of insects—most notably, blowflies—as a body changes during decomposition allow investigators to estimate time of death. Benbow and his colleagues are endeavoring to apply those same principles to the necrobiome – the collection of microorganisms inside a dead body.

“After something dies, the microbial community within it changes,” Benbow said. “If we can understand how that community changes, and if we can find consistent patterns of change within it, then we may be able to use them to determine when a death occurred—just like with insects.”

To determine those patterns, Benbow has to examine the population of not just one type of bacteria in the body but the entire microbial community. In humans, this comprises hundreds of species. The team is also maintaining a database of the findings, which is available to U.S. researchers and investigators to access and apply to their own work.

Studying changes in the necrobiome of other species has implications for human cases. Courtney Weatherbee, a graduate student in the MSU Department of Entomology, spent the summer identifying patterns in the changing microbiome of dead pigs. The work, done in partnership with researchers at Purdue University, followed up on similar research conducted by Jennifer Pechal, a fixed-term assistant professor in the Department of Entomology. It entailed sampling six pig carcasses every 12 hours for both insect and microbial life in an effort to estimate time of death.

“The collaboration we have in the lab both between our own researchers and with those at other institutions is incredibly valuable,” Weatherbee said. “It allows us to pursue some pretty ambitious projects that have an impact on the world.”

Though Weatherbee has only begun to scratch the surface of the data she collected, preliminary findings suggest that the time of death can be accurately determined by measuring the microbial community. This adds an important line of evidence to Benbow’s work and validates Pechal’s previous study.

Adding another tool to the investigator’s crime scene repertoire, although a daunting task, will have far-reaching benefits in an era when juries increasingly expect genetic evidence in trials.

“We’ve seen—through the influence of television shows such as ‘CSI’—where the characters can take a swab from a dead body and in the span of 45 minutes catch a killer. Jurors now have started demanding physical or chemical evidence as part of a prosecutor’s case,” Benbow explained. “When that isn’t available, I’ve been told by several prosecutors and expert witnesses that it’s much harder for them to make their case. We’re adding another avenue of evidence they can pursue at a crime scene.”

The ecological impact of death

The forensic efforts cross species lines, having implications well beyond homicides. Since 2013, through a partnership with the U.S. Department of Agriculture and Texas A & M University, Benbow has been studying the changing microbiome of dead salmon in streams near Juneau, Alaska.

In gathering data on how the microbial community changes over time as a salmon carcass decays, Benbow hopes to identify patterns that he can compare to those in other organisms, such as the humans involved in the Wayne County project. As commonalities appear, Benbow’s findings could be applied to other fields, such as natural resources management and law enforcement.

“If we can understand how the microbial community changes in a fish or a human, we can start to understand how it changes in a wide range of organisms,” Benbow said. “You could apply it to issues such as poaching. If the police find someone who has killed a bear, for example, and that person claims it charged and he/she shot it out of self-defense, the police could examine the bear’s microbiome to determine a time of death and whether the timeline of the suspect’s story is consistent with the evidence.”